US20090266334A1 - General purpose internal combustion engine - Google Patents
General purpose internal combustion engine Download PDFInfo
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- US20090266334A1 US20090266334A1 US12/383,168 US38316809A US2009266334A1 US 20090266334 A1 US20090266334 A1 US 20090266334A1 US 38316809 A US38316809 A US 38316809A US 2009266334 A1 US2009266334 A1 US 2009266334A1
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- throttle valve
- choke valve
- fully
- closing mechanism
- choke
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Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D9/00—Controlling engines by throttling air or fuel-and-air induction conduits or exhaust conduits
- F02D9/08—Throttle valves specially adapted therefor; Arrangements of such valves in conduits
- F02D9/10—Throttle valves specially adapted therefor; Arrangements of such valves in conduits having pivotally-mounted flaps
- F02D9/109—Throttle valves specially adapted therefor; Arrangements of such valves in conduits having pivotally-mounted flaps having two or more flaps
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D9/00—Controlling engines by throttling air or fuel-and-air induction conduits or exhaust conduits
- F02D9/08—Throttle valves specially adapted therefor; Arrangements of such valves in conduits
- F02D9/10—Throttle valves specially adapted therefor; Arrangements of such valves in conduits having pivotally-mounted flaps
- F02D9/1065—Mechanical control linkage between an actuator and the flap, e.g. including levers, gears, springs, clutches, limit stops of the like
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M35/00—Combustion-air cleaners, air intakes, intake silencers, or induction systems specially adapted for, or arranged on, internal-combustion engines
- F02M35/10—Air intakes; Induction systems
- F02M35/10006—Air intakes; Induction systems characterised by the position of elements of the air intake system in direction of the air intake flow, i.e. between ambient air inlet and supply to the combustion chamber
- F02M35/10026—Plenum chambers
- F02M35/10032—Plenum chambers specially shaped or arranged connecting duct between carburettor or air inlet duct and the plenum chamber; specially positioned carburettors or throttle bodies with respect to the plenum chamber
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M35/00—Combustion-air cleaners, air intakes, intake silencers, or induction systems specially adapted for, or arranged on, internal-combustion engines
- F02M35/10—Air intakes; Induction systems
- F02M35/10006—Air intakes; Induction systems characterised by the position of elements of the air intake system in direction of the air intake flow, i.e. between ambient air inlet and supply to the combustion chamber
- F02M35/10078—Connections of intake systems to the engine
- F02M35/10085—Connections of intake systems to the engine having a connecting piece, e.g. a flange, between the engine and the air intake being foreseen with a throttle valve, fuel injector, mixture ducts or the like
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M35/00—Combustion-air cleaners, air intakes, intake silencers, or induction systems specially adapted for, or arranged on, internal-combustion engines
- F02M35/10—Air intakes; Induction systems
- F02M35/1015—Air intakes; Induction systems characterised by the engine type
- F02M35/1017—Small engines, e.g. for handheld tools, or model engines; Single cylinder engines
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M35/00—Combustion-air cleaners, air intakes, intake silencers, or induction systems specially adapted for, or arranged on, internal-combustion engines
- F02M35/10—Air intakes; Induction systems
- F02M35/10242—Devices or means connected to or integrated into air intakes; Air intakes combined with other engine or vehicle parts
- F02M35/10255—Arrangements of valves; Multi-way valves
Definitions
- This invention relates to a general-purpose internal combustion engine, particularly to a general-purpose internal combustion engine equipped with an actuator for driving a throttle valve.
- electronically-controlled throttle apparatuses (electronically-controlled governors) utilizing an actuator such as a stepper motor to open and close a throttle valve for accurately controlling engine speed have been applied to general-purpose internal combustion engines used as prime movers in generators, agricultural machines and various other equipment.
- An object of this invention is therefore to overcome this problem by providing a general-purpose internal combustion engine having a choke valve opening/closing mechanism that can move a choke valve without need to install an additional actuator.
- this invention provides a general-purpose internal combustion engine having a throttle valve and a choke valve each installed in an air intake passage connected to a combustion chamber, air sucked in flowing through the air intake passage and mixing with fuel to generate an air-fuel mixture that enters the combustion chamber of a cylinder and is ignited to drive a piston to rotate a crankshaft to be connected to a load, comprising: an actuator; a throttle valve opening/closing mechanism connected to the actuator to open/close the throttle valve; and a choke valve opening/closing mechanism connected to the throttle valve opening/closing mechanism to open/close the choke valve in response to operation of the throttle valve opening/closing mechanism.
- FIG. 1 is an overall view of a general-purpose internal combustion engine according to a first embodiment of this invention
- FIG. 2 is an enlarged cross-sectional view of a carburetor shown in FIG. 1 ;
- FIG. 3 is a plan view of the carburetor shown in FIG. 2 when a cover of a motor case is removed;
- FIG. 4 is an explanatory view showing the configuration of an electronic control unit and combination switch shown in FIG. 1 ;
- FIG. 5 is an explanatory view showing the characteristics of opening and closing operation of a throttle valve and choke valve shown in FIG. 1 etc.;
- FIG. 6 is a view, similar to FIG. 3 , showing the carburetor shown in FIG. 2 ;
- FIG. 7 is a view, similar to FIG. 3 , showing the carburetor shown in FIG. 2 ;
- FIG. 8 is a flowchart showing the processing of controlling the operation of a throttle valve actuator at starting of the engine shown in FIG. 1 ;
- FIG. 9 is a flowchart showing the processing of controlling the operation of the throttle valve actuator when the engine shown in FIG. 1 is stopped;
- FIG. 10 is a plan view, similar to FIG. 3 , but showing a carburetor of a general-purpose internal combustion engine according to a second embodiment of this invention.
- FIG. 11 is a view, similar to FIG. 10 , showing the carburetor shown in FIG. 10 ;
- FIG. 12 is a view, similar to FIG. 10 , showing the carburetor shown in FIG. 10 ;
- FIG. 13 is a flowchart showing the processing of controlling the operation of an actuator of the throttle valve etc., at starting of the engine;
- FIG. 14 is a flowchart showing the processing of controlling the operation of the actuator of the throttle valve etc., when the engine is stopped.
- FIG. 15 is a perspective view showing the vicinity of an air intake passage of a general-purpose internal combustion engine according to a third embodiment of this invention.
- FIG. 1 is an overall view of a general-purpose internal combustion engine according to a first embodiment.
- Reference numeral 10 in FIG. 1 designates a general-purpose internal combustion engine (hereinafter simply called “engine”).
- the engine 10 is an air-cooled, four-cycle, single-cylinder OHV model with a displacement of, for example, 440 cc.
- the engine 10 is suitable for use as the prime mover of a generator, agricultural machine or any of various other kinds of equipment.
- the engine 10 has a cylinder 12 accommodating a piston 14 that can reciprocate therein.
- An intake valve 20 and exhaust valve 22 are installed so as to face a combustion chamber 16 of the engine 10 for opening and closing communication between the combustion chamber 16 and an intake port 24 or exhaust port 26 .
- a temperature sensor 28 is disposed near the cylinder 12 for producing an output indicating the temperature of the engine 10 .
- the piston 14 is connected to a crankshaft 30 that is connected to a camshaft 34 through a gear mechanism 32 for the camshaft 34 .
- One end of the crankshaft 30 is connected with a load (not shown) such as a generator and the other end thereof with a flywheel 36 .
- the flywheel 36 is installed with magnet pieces 38 on its inside surface. Also on the inside of the flywheel 36 , a power coil (generation coil) 40 and a fuel-cut solenoid valve coil (FS coil; shown in FIG. 4 which will be described later) are fastened to the engine body to face the magnet pieces 38 and on the outside of the flywheel 36 , a pulsar coil 42 is fastened to the engine body to face the magnet pieces 38 .
- the power coil 40 , pulsar coil 42 and FS coil produce outputs, i.e., alternating current synchronous with rotation of the crankshaft 30 .
- the crankshaft 30 is attached with a recoil starter 44 that starts the engine 10 when manually manipulated or operated by the operator.
- a carburetor 46 is connected to the intake port 24 .
- FIG. 2 is an enlarged cross-sectional view of the carburetor 46 shown in FIG. 1 .
- the carburetor 46 unitarily comprises an air intake passage 50 , motor case 52 and carburetor assembly 54 .
- the downstream side of the air intake passage 50 is connected through an insulator 56 to the intake port 24 , and the upstream side thereof is connected through an air-cleaner elbow 58 to an air-cleaner (not shown).
- a throttle valve 60 is installed in the air intake passage 50 and a choke valve 62 is also installed in the air intake passage 50 on the upstream side of the throttle valve 60 .
- the air intake passage 50 is reduced in diameter between the throttle valve 60 and choke valve 62 to form a venturi 64 .
- the motor case 52 is attached with a cover 66 and the internal space formed by the motor case 52 and cover 66 is disposed with an electric motor (actuator) 70 for driving the throttle valve 60 and choke valve 62 .
- the motor 70 is a stepper motor having a rotor and a stator wound with a coil and connected to the throttle valve 60 via a throttle valve opening/closing mechanism (gear mechanism) 72 .
- FIG. 3 is a plan view of the carburetor 46 shown in FIG. 2 when the cover 66 of the motor case 52 is removed.
- FIG. 3 shows the status where the throttle valve 60 is at the fully-closed position and the choke valve 62 is at the fully-opened position, as indicated by imaginary lines.
- the throttle valve opening/closing mechanism 72 includes four gears that are all external gears. Specifically, an output shaft 70 S of the motor 70 is attached with a first gear 74 and the first gear 74 is engaged with a second gear 76 which is rotatably supported in the motor case 52 .
- a third gear (eccentric gear) 78 is installed coaxially with the second gear 76 to be integrally rotatable therewith. As can be seen in FIG. 3 , the third gear 78 is formed with teeth only on a part of its circumference (where a fourth gear (explained later) is to be engaged).
- the third gear 78 is engaged with the fourth gear (eccentric gear; now assigned by 82 ) connected to a throttle shaft 80 that supports the throttle valve 60 .
- the output of the motor 70 is reduced in speed in accordance with gear ratios of the gears 74 , 76 , 78 , 82 and transmitted to the throttle shaft 80 to open and close the throttle valve 60 .
- the mechanism 72 is configured to open and close the throttle valve 60 within a range between the fully-closed position and a position over or beyond the fully-opened position by predetermined opening, i.e., a position set over the fully-opened position in the opening direction by the predetermined opening, in response to the operation of the motor 70 . This will be explained later.
- the throttle shaft 80 is installed on its circumference with a throttle return spring 84 (shown in FIG. 2 ) that is constituted of a torsion coil spring.
- a throttle return spring 84 shown in FIG. 2
- One end of the spring 84 is connected to the fourth gear 82 attached to the throttle shaft 80 and the other end thereof is connected to a hook pin 86 (shown in FIG. 2 ) projected in the motor case 52 .
- Winding of the spring 84 is set in the direction in which the throttle valve 60 is opened via the throttle shaft 80 .
- the throttle valve opening/closing mechanism 72 is connected with the choke valve 62 through a choke valve opening/closing mechanism 90 . Therefore, the motor 70 is connected to the throttle valve 60 through the mechanism 72 and to the choke valve 62 through the mechanisms 72 , 90 .
- the choke valve opening/closing mechanism 90 comprises an arm 94 that is attached to a choke shaft 92 supporting the choke valve 62 for rotating the shaft 92 , and a link 96 that connects the arm 94 with the mechanism 72 (precisely, the third gear 78 thereof).
- the link 96 is supported to be rotatable about a rotation shaft 100 in the motor case 52 .
- the link 96 is provided at its end (one end) 96 a on the arm 94 side with a first pin 96 b that extends upward in FIG. 2 .
- the first pin 96 b is inserted through a long hole 94 a bored in the arm 94 .
- the link 96 is also provided at its end (the other end) 96 c on the third gear 78 side with a second pin 96 d that extends upward in FIG. 2 .
- the second pin 96 d abuts on the circumference of the third gear 78 at a portion not formed with teeth.
- the portion of the circumference of the third gear 78 where no teeth is formed i.e., where the second pin 96 d abuts
- the portion of the circumference of the third gear 78 where the concavity is formed is called the “first abutment portion” and assigned by 78 a.
- the remaining portion of the circumference of the third gear 78 where no teeth is formed other than the first abutment portion 78 a is called the “second abutment portion” and assigned by 78 b. Positions formed with the first and second abutment portions 78 a, 78 b on the circumference of the third gear 78 will be described later.
- a choke return spring 102 is installed on the circumference of the choke shaft 92 .
- the spring 102 is constituted of a torsion coil spring, similarly to the throttle return spring 84 .
- One end of the choke return spring 102 is connected to the arm 94 and the other end thereof to a hook pin 104 that projects in the motor case 52 . Winding of the spring 102 is set in the direction in which the choke valve 62 is closed via the choke shaft 92 .
- the choke valve opening/closing mechanism 90 is configured to include the spring 102 that urges the choke valve 62 in the closing direction (toward the fully-closed position), the urging force is transmitted to the link 96 through the arm 94 .
- counterclockwise force about the rotation shaft 100 acts on the link 96 so that the second pin 96 d of the link 96 constantly abuts, as being pressed, on the circumference (i.e., the first or second abutment portion 78 a, 78 b ) of the third gear 78 .
- the one end 96 a of the link 96 is connected to the choke shaft 92 through the first pin 96 b and arm 94 , and the other end 96 c thereof to (abuts on) the throttle valve opening/closing mechanism 72 (precisely, the first or second abutment portion 78 a, 78 b of the third gear 78 ) through the second pin 96 d.
- the carburetor assembly 54 comprises a float chamber connected to a fuel tank, a main nozzle connected to the float chamber through a main jet and main fuel passage, and an idle port and a slow port both connected to a slow fuel passage that is branched from the main fuel passage.
- the main nozzle is installed at a position where it faces into the venturi 64 and the idle port and slow port are installed at positions where they face into the vicinity of the throttle valve 60 .
- the reference numeral 106 in FIG. 2 designates a fuel-cut solenoid valve (FS valve).
- a valve member (not shown) of the FS valve 106 is disposed between the float chamber and main jet and, when a coil (shown in FIG. 4 ; explained later) is energized, is closed for blocking passage of fuel.
- the air-fuel mixture thus produced passes through the intake port 24 and intake valve 20 to be sucked into the combustion chamber 16 .
- the sucked air-fuel mixture is ignited by an spark plug (shown in FIG. 4 ; explained later) to burn and the resulting combustion gas is discharged to the exterior of the engine 10 through the exhaust valve 22 , exhaust port 26 , a muffler (not shown) and the like.
- the engine 10 has the throttle valve 60 and choke valve 62 each installed in the air intake passage 50 connected to the combustion chamber 16 , and air sucked in flows through the air intake passage 60 and mixes with fuel supplied by the carburetor 46 to generate the air-fuel mixture that enters the combustion chamber 16 of the cylinder 12 and is ignited to drive the piston 14 to rotate the crankshaft 30 to be connected to a load such as a generator.
- An engine speed setting switch 110 is installed to be manipulated by the operator and produces an output or signal indicative of desired engine speed in response to the manipulation by the operator.
- the outputs of the above-mentioned temperature sensor 28 , power coil 40 , pulsar coil 42 and the engine speed setting switch 110 are sent to an electronic control unit (ECU) 112 that is constituted as a microcomputer.
- ECU electronice control unit
- a combination switch 114 is also installed to be manipulated by the operator.
- the combination switch 114 is connected to the ECU 112 . Based on the operator's manipulation of the combination switch 114 and the other inputs, the ECU 112 controls the operation of the engine 10 (e.g., the operation of the electric motor 70 ).
- FIG. 4 is an explanatory view showing the configuration of the ECU 112 and the combination switch 114 .
- the ECU 112 is equipped with a rectification circuit 116 , engine speed (NE) detection circuit 120 and control circuit 122 .
- the output of the power coil 40 is inputted to the rectification circuit 116 , where it is converted to 12V direct current to be supplied as operating power to the components of the engine 10 , such as the ECU 112 , through a circuit (not shown).
- the output of the power coil 40 is also sent to the engine speed detection circuit 120 , where it is converted to a pulse signal.
- the pulse signal is inputted to the control circuit 122 for detecting the engine speed.
- the ECU 112 is further equipped with a signal shaping circuit 124 and an ignition circuit 126 .
- the output of the pulsar coil 42 is inputted to the signal shaping circuit 124 , where it is formed as the ignition signal synchronous with rotation of the crankshaft 30 and then sent to the ignition circuit 126 and control circuit 122 .
- the combination switch 114 comprises first and second switches 114 a, 114 b.
- the solid lines indicate the state of the switches 114 a, 114 b when the combination switch 114 is in the OFF position and the imaginary lines indicate their state when it is in the ON position.
- the first switch 114 a is interposed between the FS coil (now assigned by 130 ) and the FS valve (precisely, the valve thereof) 106 .
- the second switch 114 b is turned ON, the 12V direct current generated from the output of the power coil 40 is inputted to the control circuit 122 and a DC/DC converter 132 .
- the DC/DC converter 132 is connected to the primary coil of an ignition coil 136 through a capacitor 134 for charging the capacitor 134 .
- the secondary coil of the ignition coil 136 is connected to the spark plug (now assigned by 140 ) and the capacitor 134 is grounded via a thyristor 142 .
- the ignition circuit 126 applies current to the gate of the thyristor 142 in response to an ignition signal from the signal shaping circuit 124 or control circuit 122 , so that the capacitor 134 discharges to energize the primary coil of the ignition coil 136 .
- the resulting high voltage generated in the secondary coil produces spark between electrodes of the spark plug 140 , thereby igniting the air-fuel mixture in the combustion chamber 16 .
- the above-mentioned temperature sensor 28 and engine speed setting switch 110 are connected to the control circuit 122 .
- the control circuit 122 determines desired openings of the throttle valve 60 and choke valve 62 and outputs control signals in accordance with the determined desired openings to a motor driver 144 so as to operate the motor 70 , thereby opening and closing the valves 60 , 62 to regulate the engine speed or fuel quantity to be supplied to the engine 10 .
- the first switch 114 a When the combination switch 114 is put in the ON position by the operator, the first switch 114 a is turned OFF to cut off the supply of operating current to the FS valve 106 .
- the FS valve 106 is normally open, so that cutting off the supply of operating current enables jetting of fuel from the carburetor 46 .
- the second switch 114 b is turned ON and the recoil starter 44 is operated, the resulting rotation of the crankshaft 30 causes the power coil 40 and pulsar coil 42 to produce outputs.
- 12V direct current and an ignition signal are produced (shaped) to activate the ECU 112 and start the engine 10 .
- the combination switch 114 When the combination switch 114 is put in the OFF position, the second switch 114 b is turned OFF and the supply of operating current to the control circuit 122 is cut off, whereby the control circuit 122 terminates ignition to stop the engine 10 , and the first switch 114 a is turned ON to interconnect the FS coil 130 and the FS valve 106 , thereby performing fuel cutoff.
- the FS coil 130 since rotation of the crankshaft 30 does not stop immediately after ignition is terminated, the FS coil 130 continues to generate electricity and accordingly the FS valve 106 receives operating current from the FS coil 130 and is closed (i.e., fuel cutoff is performed) for a certain period.
- FIG. 5 is an explanatory view showing the characteristics of the opening and closing operation of the throttle valve 60 and choke valve 62 .
- the motor 70 rotates the throttle shaft 80 through the first to fourth gears 74 , 76 , 78 , 82 of the mechanism 72 so as to close the throttle valve 60 to the fully-closed position shown in FIGS. 3 and 5A .
- the second pin 96 d of the link 96 abuts on the second abutment portion 78 b of the third gear 78 and the choke valve 62 is fully opened.
- the motor 70 operates the first to fourth gears 74 , 76 , 78 , 82 to rotate in the directions indicated by arrows in FIG. 6 to rotate the throttle shaft 80 counterclockwise, thereby opening the throttle valve 60 to the fully-opened position.
- the choke valve 62 is held at the fully-opened position.
- the mechanism 90 holds the choke valve 62 at the fully-opened position.
- the motor 70 operates the mechanism 72 to displace the link 96 which moves in response thereto and rotate the choke shaft 92 , thereby opening and closing the choke valve 62 .
- the motor 70 operates the first to fourth gears 74 , 76 , 78 , 82 to rotate in the directions indicated by arrows in FIG. 7 to further rotate the throttle shaft 80 counterclockwise, thereby opening the throttle valve 60 to a position over or beyond the fully-opened position by predetermined opening a, which position is hereinafter called the “over-fully-opened position.”
- the second pin 96 d slides to the first abutment portion 78 a by the rotation of the third gear 78 . It causes the link 96 to displace or rotate about the rotation shaft 100 in the counterclockwise direction, so that the first pin 96 b, while sliding in the long hole 94 a, displaces the arm 94 .
- the displacement of the arm 94 makes the choke shaft 92 rotate clockwise in the drawing, thereby closing the choke valve 62 to the fully-closed position as shown in FIG. 5C .
- the locations in the third gear 78 formed with the first and second abutment portions 78 a, 78 b are determined such that, when the second pin 96 d abuts on the second abutment portion 78 b (as shown, for example, in FIGS. 3 and 6 ), the choke valve 62 is positioned at the fully-opened position, while the third gear 78 is rotated clockwise in the drawing by the motor 70 , and when the second pin 96 d abuts on the first abutment portion 78 a (as shown in FIG. 7 , for example), the choke valve 62 is positioned at the fully-closed position.
- the choke valve opening/closing mechanism 90 opens and closes the choke valve 62 in response to the movement of the throttle valve opening/closing mechanism 72 . More specifically, when the throttle valve 60 is positioned between the fully-closed position and the fully-opened position, the mechanism 90 holds the choke valve 62 at the fully-opened position, and when the throttle valve 60 is positioned between the fully-opened position and the over-fully-opened position, it opens and closes the choke valve 62 within a range between the fully-opened position and the fully-closed position.
- the movement of the choke valve 62 is explained using two kinds of positions, i.e., the fully-opened position and the fully-closed position. Since the first abutment portion 78 a is formed in the concave shape, the choke valve 62 can be regulated to achieve a given opening by appropriately regulating a position where the second pin 96 d abuts on the first abutment portion 78 a. In other words, the choke valve 62 can be opened and closed between the fully-opened position and the fully-closed position by properly regulating the opening of the throttle valve 60 between the fully-opened position and the over-fully-opened position.
- FIG. 8 is a flowchart showing the processing of this operation of the motor 70 executed by the ECU 112 .
- the illustrated program is executed only once at engine start.
- the throttle valve 60 and choke valve 62 are positioned as shown in FIGS. 7 and 5C before the engine 10 is started, specifically the throttle valve 60 is at the over-fully-opened position due to the urging force by the throttle return spring 84 and the choke valve 62 is at the fully-closed position by the choke return spring 102 .
- the operation of the motor 70 is controlled so as to move (open and close) the throttle valve 60 between the over-fully-opened position and the fully-opened position.
- the throttle valve 60 is moved as mentioned above to open and close the choke valve 62 between the fully-closed position and the fully-opened position, as shown in FIGS. 5B , 5 C.
- the air-fuel mixture in the air intake passage 50 is made rich (i.e., the rich air-fuel mixture condition is established), thereby improving the starting performance of the engine 10 .
- S 12 it is determined whether choking is required, i.e., whether the warm-up operation has been completed and the rich air-fuel mixture condition should be terminated.
- the determination in S 12 is made based on the output of the engine speed detection circuit 120 and, when the engine speed exceeds a predetermined value (e.g., 3000 rpm), it is discriminated that the choking is not required.
- a predetermined value e.g., 3000 rpm
- the program returns to S 10 and when the result is Yes, the program proceeds to S 14 , in which the normal control of the throttle valve 60 is conducted to terminate the rich air-fuel mixture condition, which is produced by the choke valve 62 .
- the operation of the motor 70 is controlled so as to move the throttle valve 60 between the fully-closed position and the fully-opened position (i.e., move the throttle valve 60 at desired opening for maintaining the desired engine speed inputted through the engine speed setting switch 110 ). Since the throttle valve 60 is moved between the fully-closed position and the fully-opened position, as shown in FIGS. 5A , 5 B, the choke valve 62 is held at the fully-opened position, thereby terminating the rich air-fuel mixture condition produced by the choke valve 62 .
- FIG. 9 is a flowchart showing the processing of this operation of the motor 70 executed by the ECU 112 .
- the illustrated program is executed at predetermined interval, e.g., 100 milliseconds.
- S 100 it is determined whether an instruction to stop the engine 10 is inputted, specifically the combination switch 114 is put in the OFF position.
- the program proceeds to S 102 , in which the operation of the motor 70 is controlled so that the throttle valve 60 is moved (opened) to the over-fully-opened position.
- the throttle valve 60 is thus moved to close the choke valve 62 to the fully-closed position, as shown in FIG. 5C , for preparing for the next engine start.
- the engine according to the first embodiment since the engine according to the first embodiment is thus configured, it becomes possible to move the choke valve 62 by the motor 70 adapted to move the throttle valve 60 , i.e., move both the throttle valve 60 and the choke valve 62 solely by the motor 70 . Owing to this configuration, the choke valve 62 can be moved without the need of another motor, saving space to be required for installment of another motor. Further, an electric motor for the choke valve, an associated motor driver (drive circuit), which are utilized in the prior art '838 and indicated by imaginary lines in FIG. 4 , and other equipment such as a harness can be removed, thereby achieving decrease in power consumption and cost.
- drive circuit which are utilized in the prior art '838 and indicated by imaginary lines in FIG. 4 , and other equipment such as a harness
- FIG. 10 is a view, similar to FIG. 3 , but showing a carburetor of the engine according to the second embodiment when the cover 66 of the motor case 52 is removed. Constituent elements corresponding to those of the first embodiment are assigned with the same reference symbols as those in the first embodiment and will not be explained.
- the motor case 52 is installed therein with a choke valve opening regulating mechanism 146 for regulating opening of the choke valve 62 .
- the mechanism 146 comprises a thermo-wax having a wax section 146 a filled with wax which expands and contracts in response to ambient temperature (precisely, wax which expands in its volume with increasing ambient temperature, while contracting with decreasing ambient temperature; not shown), a rod 146 b which is connected to the wax section 146 a and linearly displaces in response to the expansion/contraction of wax, a drive pin 146 d which is connected to the wax section 146 a through the rod 146 b and a flange 146 c and linearly displaces in response to the displace of the rod 146 b, and a case 146 e housing those components.
- FIG. 10 shows the mechanism 146 when the wax is contracted.
- a tip 146 d 1 of the drive pin 146 d projects toward the exterior through a hole 146 e 1 formed in the case 146 e and can abut on the choke valve opening/closing mechanism 90 (i.e., the link 96 thereof, more precisely, a side surface 96 e between the rotation shaft 100 and end 96 a ).
- the drive pin 146 d is normally urged by a return spring 146 f in the direction of housing the drive pin 146 d in the case 146 e, i.e., of shortening the projecting amount (length) L of the tip 146 d 1 (in the downward direction in the drawing). Therefore, the projecting amount L of the drive pin 146 d is made minimum by the urging force of the return spring 146 f when the wax is contracted (i.e., is not expanded) as shown in FIG. 10 .
- the mechanism 146 is further equipped with a heater 146 g for heating the wax section 146 a.
- the heater 146 g is composed of a heating wire made of a nichrome wire etc., an insulating material covering the wire, a protection pipe and the like.
- the heater 146 g is thus an electric heater that generates heat when being supplied with power current as operating power from the power coil 40 .
- the operation of the heater 146 g is controlled by the ECU 112 (i.e., the control circuit 122 thereof) as indicated by imaginary lines in FIGS. 1 , 4 .
- FIG. 11 shows the mechanism 146 when the wax is contracted and FIG. 12 shows that when the wax is expanded. It should be noted that the throttle valve 60 is at the over-fully-opened position in FIGS. 11 , 12 .
- the wax of the wax section 146 a is contracted and it makes the projecting amount L of the drive pin 146 d minimum.
- the drive pin 146 d does not abut or slightly abuts on the surface 96 e of the link 96 .
- the tip 146 d 1 of the drive pin 146 d does not abut on the surface 96 e under condition where the link 96 holds the choke valve 62 either at the fully-opened position ( FIG. 10 ) or at the fully-closed position ( FIG. 11 ).
- the wax is expanded to push the rod 146 b and flange 146 c upward in the drawing.
- the drive pin 146 d acts against the urging force of the return spring 146 f and is displaced upward in the drawing, thereby increasing the projecting amount L.
- the operating temperature is, for instance, set to 70° C.
- the drive pin 146 d drives the choke valve opening/closing mechanism 90 (i.e., the link 96 , arm 94 and the like) in response to the expansion/contraction of the wax, thereby regulating the opening of the choke valve 62 .
- the second embodiment is configured such that the choke valve 62 is opened and closed by the choke valve opening/closing mechanism 90 that operates in response to the operation of the throttle valve opening/closing mechanism 72 , and the opening of the choke valve 62 , which is opened and closed by the mechanism 90 , can be regulated by using the choke valve opening regulating mechanism 146 in response to ambient temperature.
- FIG. 13 is a flowchart similar to FIG. 8 , but showing the processing of this operation of the actuator executed by the ECU 112 . Note that it is assumed the engine 10 is started in the so-called “cold start” manner after a specific time period has elapsed since the last engine stop, ambient temperature around the choke valve opening regulating mechanism 146 is relatively low and the wax is contracted.
- the processing of the steps of S 200 , S 202 is conducted similarly to the first embodiment.
- the program returns to S 200 , i.e., the processing of S 200 is repeated until the determination that the choking is not required is made.
- the exhaust heat of the engine 10 increases with increasing engine speed.
- the wax is expanded to gradually project the drive pin 146 d.
- the drive pin 146 d displaces the link 96 so as to gradually rotate the choke valve 62 in the opening direction, i.e., it decreases fuel injection quantity as ambient temperature increases along with increase in the engine speed, thereby making the rich air-fuel mixture leaner gradually.
- the opening of the choke valve 62 is regulated by the mechanism 146 in response to ambient temperature.
- the normal control of the throttle valve 60 is conducted. Specifically, the operation of the motor 70 is controlled so as to move the throttle valve 60 between the fully-closed position and the fully-opened position. Since the throttle valve 60 is thus moved, the choke valve 62 is held at the fully-opened position, and it is held at the fully-opened position also by the drive pin 146 d of the mechanism 146 , so it becomes possible to prevent the choke valve 62 from closing while the engine 10 is in operation.
- FIG. 14 is a flowchart similar to FIG. 9 , but showing the processing of this operation of the actuator executed by the ECU 112 .
- S 300 it is determined whether an instruction to stop the engine 10 is inputted. When the result is No, the remaining steps are skipped and when the result is Yes, the program proceeds to S 302 , in which power supply to the heater 146 g is cut off to stop heating the wax section 146 a.
- the program then proceeds to S 304 , in which the operation of the motor 70 is controlled so that the throttle valve 60 is moved (opened) to the over-fully-opened position. Since the throttle valve 60 is thus moved, the link 96 of the choke valve opening/closing mechanism 90 is operated to close the choke valve 62 to the fully-closed position. However, the wax is still in expanded status because the power supply to the heater 146 g has been just cut off in S 302 . As a result, the drive pin 146 d projected due to the expansion of wax remains abutting on the link 96 and the choke valve 62 is held at the fully-opened position by the drive pin 146 d. Specifically, the choke valve 62 is not closed to the fully-closed position immediately after the engine 10 stops.
- the choke valve 62 stays at the fully-opened position or thereabout, thereby enabling to start the engine 10 without enriching air-fuel mixture excessively.
- the engine according to the second embodiment since the engine according to the second embodiment is thus configured, it becomes possible to prevent the air-fuel mixture from being enriched by opening the choke valve 62 when ambient temperature is relatively high in a case of, for example, hot start, specifically, the choke valve 62 can be regulated at appropriate opening in response to ambient temperature, thereby improving fuel efficiency.
- FIG. 15 is a perspective view showing the vicinity of the air intake passage 50 of the engine 10 according to the third embodiment. Constituent elements corresponding to those of the first embodiment are assigned with the same reference symbols as those in the first embodiment and will not be explained.
- fuel-cut is conducted using a fuel-cut needle valve 150 in place of the FS valve 106 , and the needle valve 150 is moved by the arm 94 .
- the choke valve 62 is manually manipulated by the operator in the third embodiment.
- the needle valve 150 is connected to the arm 94 and a jet orifice 152 a of a main nozzle 152 can be sealed in response to rotation (displacement) of the arm 94 . More specifically, when the throttle valve 60 is at a position between the fully-closed position and the fully-opened position, the needle valve 150 is positioned to make the jet orifice 152 a open for enabling fuel to inject from the main nozzle 152 . On the other hand, when the throttle valve 60 is moved to the over-fully-opened position, the arm 94 is rotated to move the needle valve 150 downward in the drawing so as to seal the jet orifice 152 a, thereby cutting off supply of fuel.
- the needle valve 150 when the throttle valve 60 is moved between the fully-closed position and the fully-opened position, i.e., the throttle valve 60 is normally operated, the needle valve 150 is positioned to make the jet orifice 152 a open, thereby enabling fuel to inject from the main nozzle 152 .
- the needle valve 150 In a case where the throttle valve 60 is configured to move to the over-fully-opened position when the engine 10 is stopped, the needle valve 150 is moved downward so as to seal the jet orifice 152 a, thereby cutting off fuel supply.
- the engine according to the third embodiment is configured such that the motor 70 moves both the throttle valve 60 and the fuel-cut needle valve 150 .
- the needle valve 150 can be moved without the need of another electric motor, saving space to be required for installment of a motor for the needle valve 150 .
- the first to second embodiments are configured to have a general-purpose internal combustion engine having a throttle valve ( 60 ) and a choke valve ( 62 ) each installed in an air intake passage ( 50 ) connected to a combustion chamber ( 16 ), air sucked in flowing through the air intake passage mixes with fuel to generate an air-fuel mixture that enters the combustion chamber of a cylinder ( 12 ) and ignited to drive a piston ( 14 ) to rotate a crankshaft ( 30 ) to be connected to a load, comprising: an actuator (electric motor 70 ), a throttle valve opening/closing mechanism ( 72 ) connected to the actuator to open/close the throttle valve; and a choke valve opening/closing mechanism ( 90 ) connected to the throttle valve opening/closing mechanism to open/close the choke valve in response to operation of the throttle valve opening/closing mechanism.
- the throttle valve opening/closing mechanism opens/closes the throttle valve within a range between a fully-closed position and an over-fully-opened position over a fully-opened position by predetermined opening a in response to the operation of the actuator, and the choke valve opening/closing mechanism holds the choke valve at a fully-opened position when the throttle valve is positioned between the fully-closed position and the fully-opened position, while opening/closing the choke valve within a range between the fully-opened position and a fully-closed position when the throttle valve is positioned between the fully-opened position and the over-fully-opened position.
- the throttle valve opening/closing mechanism comprises a plurality of gears ( 74 , 76 , 78 , 82 ). With this, the throttle valve opening/closing mechanism can be simple in structure.
- the throttle valve opening/closing mechanism comprises at least a first gear ( 74 ) connected to an output shaft ( 70 S) of the actuator and a second gear ( 76 ) engaged with the first gear.
- the throttle valve opening/closing mechanism can be simple in structure.
- the choke valve opening/closing mechanism comprises a link ( 96 ) connected at its one end with a choke shaft ( 92 ) that supports the choke valve and at its other end with the throttle valve opening/closing mechanism, the link being adapted to displaced in response to the operation of the throttle valve opening/closing mechanism to rotate the choke shaft to open/close the choke valve.
- the engine according to the second embodiment further includes: a choke valve opening regulating mechanism that regulates opening of the choke valve opened/closed by the choke valve opening/closing mechanism in response to ambient temperature.
- a choke valve opening regulating mechanism that regulates opening of the choke valve opened/closed by the choke valve opening/closing mechanism in response to ambient temperature.
- the choke valve opening regulating mechanism comprises a wax section ( 146 a ) filled with wax that is adapted to expand/contract in response to the ambient temperature, a drive pin ( 146 d ) connected to the wax section, the drive pin driving the choke valve opening/closing mechanism in response to expansion/contraction of the wax to regulate the opening of the choke valve.
- the choke valve opening/closing mechanism further includes a heater ( 146 g ) that heats the wax section.
- the choke valve 62 stays at the fully-opened position or thereabout, thereby enabling to further improve fuel efficiency without enriching air-fuel mixture excessively.
- the engine according to the second embodiment further includes: a heating stopper that stops the heater from heating the wax section when an operator inputs an instruction to stop the engine (S 302 ). With this, it becomes possible to efficiently heat the wax section 146 a in response to the operating condition of the engine 10 .
- the engine according to the first to third embodiments further includes: an actuator controller that controls operation of the actuator such that the throttle valve is opened to the over-fully-opened position when an operator inputs an instruction to stop the engine (S 304 ). With this, it becomes possible to close the choke valve 62 to the fully-closed position when the engine 10 stops, thereby improving the starting performance of the engine 10 .
- the actuator is an electric motor, the above-mentioned effects can be achieved with simple structure.
- the actuator (motor 70 ) for opening and closing the throttle valve 60 and the like is exemplified as a stepper motor in the foregoing description, it can instead be any of various other kinds of electric motor, electromagnetic solenoid, or hydraulic equipment that is operated by driving its pump by a motor.
- a cock valve for performing fuel cut-off can instead be moved, for instance.
- fuel is supplied by the carburetor 46 , it is not limited thereto and an injector (fuel injection valve) can be disposed at the intake port 24 for supplying fuel.
- injector fuel injection valve
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Means For Warming Up And Starting Carburetors (AREA)
- Control Of Throttle Valves Provided In The Intake System Or In The Exhaust System (AREA)
Abstract
Description
- 1. Field of the Invention
- This invention relates to a general-purpose internal combustion engine, particularly to a general-purpose internal combustion engine equipped with an actuator for driving a throttle valve.
- 2. Description of the Related Art
- Conventionally, electronically-controlled throttle apparatuses (electronically-controlled governors) utilizing an actuator such as a stepper motor to open and close a throttle valve for accurately controlling engine speed have been applied to general-purpose internal combustion engines used as prime movers in generators, agricultural machines and various other equipment.
- In recent years, there is proposed a technique for improving engine starting performance by employing an automatic choke apparatus that uses an actuator to open and close a choke valve of a general-purpose engine so as to close the choke valve at cold start or the like for producing a rich air-fuel mixture. When the automatic choke apparatus is applied to the above-mentioned engine, in addition to the actuator for the throttle valve, the engine will need another actuator for the choke valve, as taught, for example, by Japanese Laid-Open Patent Application No. 2007-23838 (paragraphs 0022, 0036, FIG. 2, etc.).
- However, the additional installation of an actuator for the choke valve as set forth in the prior art requires an extra space for the installment of the actuator and the like, disadvantageously increasing the size of the entire engine.
- An object of this invention is therefore to overcome this problem by providing a general-purpose internal combustion engine having a choke valve opening/closing mechanism that can move a choke valve without need to install an additional actuator.
- In order to achieve the object, this invention provides a general-purpose internal combustion engine having a throttle valve and a choke valve each installed in an air intake passage connected to a combustion chamber, air sucked in flowing through the air intake passage and mixing with fuel to generate an air-fuel mixture that enters the combustion chamber of a cylinder and is ignited to drive a piston to rotate a crankshaft to be connected to a load, comprising: an actuator; a throttle valve opening/closing mechanism connected to the actuator to open/close the throttle valve; and a choke valve opening/closing mechanism connected to the throttle valve opening/closing mechanism to open/close the choke valve in response to operation of the throttle valve opening/closing mechanism.
- The above and other objects and advantages of the invention will be more apparent from the following description and drawings in which:
-
FIG. 1 is an overall view of a general-purpose internal combustion engine according to a first embodiment of this invention; -
FIG. 2 is an enlarged cross-sectional view of a carburetor shown inFIG. 1 ; -
FIG. 3 is a plan view of the carburetor shown inFIG. 2 when a cover of a motor case is removed; -
FIG. 4 is an explanatory view showing the configuration of an electronic control unit and combination switch shown inFIG. 1 ; -
FIG. 5 is an explanatory view showing the characteristics of opening and closing operation of a throttle valve and choke valve shown inFIG. 1 etc.; -
FIG. 6 is a view, similar toFIG. 3 , showing the carburetor shown inFIG. 2 ; -
FIG. 7 is a view, similar toFIG. 3 , showing the carburetor shown inFIG. 2 ; -
FIG. 8 is a flowchart showing the processing of controlling the operation of a throttle valve actuator at starting of the engine shown inFIG. 1 ; -
FIG. 9 is a flowchart showing the processing of controlling the operation of the throttle valve actuator when the engine shown inFIG. 1 is stopped; -
FIG. 10 is a plan view, similar toFIG. 3 , but showing a carburetor of a general-purpose internal combustion engine according to a second embodiment of this invention; -
FIG. 11 is a view, similar toFIG. 10 , showing the carburetor shown inFIG. 10 ; -
FIG. 12 is a view, similar toFIG. 10 , showing the carburetor shown inFIG. 10 ; -
FIG. 13 is a flowchart showing the processing of controlling the operation of an actuator of the throttle valve etc., at starting of the engine; -
FIG. 14 is a flowchart showing the processing of controlling the operation of the actuator of the throttle valve etc., when the engine is stopped; and -
FIG. 15 is a perspective view showing the vicinity of an air intake passage of a general-purpose internal combustion engine according to a third embodiment of this invention. - A general-purpose internal combustion engine according to preferred embodiments of the present invention will now be explained with reference to the attached drawings.
-
FIG. 1 is an overall view of a general-purpose internal combustion engine according to a first embodiment. -
Reference numeral 10 inFIG. 1 designates a general-purpose internal combustion engine (hereinafter simply called “engine”). Theengine 10 is an air-cooled, four-cycle, single-cylinder OHV model with a displacement of, for example, 440 cc. Theengine 10 is suitable for use as the prime mover of a generator, agricultural machine or any of various other kinds of equipment. - The
engine 10 has acylinder 12 accommodating apiston 14 that can reciprocate therein. Anintake valve 20 andexhaust valve 22 are installed so as to face acombustion chamber 16 of theengine 10 for opening and closing communication between thecombustion chamber 16 and anintake port 24 orexhaust port 26. Atemperature sensor 28 is disposed near thecylinder 12 for producing an output indicating the temperature of theengine 10. - The
piston 14 is connected to acrankshaft 30 that is connected to acamshaft 34 through agear mechanism 32 for thecamshaft 34. One end of thecrankshaft 30 is connected with a load (not shown) such as a generator and the other end thereof with aflywheel 36. - The
flywheel 36 is installed withmagnet pieces 38 on its inside surface. Also on the inside of theflywheel 36, a power coil (generation coil) 40 and a fuel-cut solenoid valve coil (FS coil; shown inFIG. 4 which will be described later) are fastened to the engine body to face themagnet pieces 38 and on the outside of theflywheel 36, apulsar coil 42 is fastened to the engine body to face themagnet pieces 38. Thepower coil 40,pulsar coil 42 and FS coil produce outputs, i.e., alternating current synchronous with rotation of thecrankshaft 30. Thecrankshaft 30 is attached with arecoil starter 44 that starts theengine 10 when manually manipulated or operated by the operator. - A
carburetor 46 is connected to theintake port 24. -
FIG. 2 is an enlarged cross-sectional view of thecarburetor 46 shown inFIG. 1 . - As shown in
FIG. 2 , thecarburetor 46 unitarily comprises anair intake passage 50,motor case 52 andcarburetor assembly 54. The downstream side of theair intake passage 50 is connected through aninsulator 56 to theintake port 24, and the upstream side thereof is connected through an air-cleaner elbow 58 to an air-cleaner (not shown). Athrottle valve 60 is installed in theair intake passage 50 and achoke valve 62 is also installed in theair intake passage 50 on the upstream side of thethrottle valve 60. Theair intake passage 50 is reduced in diameter between thethrottle valve 60 andchoke valve 62 to form aventuri 64. - The
motor case 52 is attached with acover 66 and the internal space formed by themotor case 52 andcover 66 is disposed with an electric motor (actuator) 70 for driving thethrottle valve 60 andchoke valve 62. Specifically, themotor 70 is a stepper motor having a rotor and a stator wound with a coil and connected to thethrottle valve 60 via a throttle valve opening/closing mechanism (gear mechanism) 72. -
FIG. 3 is a plan view of thecarburetor 46 shown inFIG. 2 when thecover 66 of themotor case 52 is removed.FIG. 3 shows the status where thethrottle valve 60 is at the fully-closed position and thechoke valve 62 is at the fully-opened position, as indicated by imaginary lines. - As shown in
FIGS. 2 and 3 , the throttle valve opening/closing mechanism 72 includes four gears that are all external gears. Specifically, anoutput shaft 70S of themotor 70 is attached with afirst gear 74 and thefirst gear 74 is engaged with asecond gear 76 which is rotatably supported in themotor case 52. A third gear (eccentric gear) 78 is installed coaxially with thesecond gear 76 to be integrally rotatable therewith. As can be seen inFIG. 3 , thethird gear 78 is formed with teeth only on a part of its circumference (where a fourth gear (explained later) is to be engaged). - The
third gear 78 is engaged with the fourth gear (eccentric gear; now assigned by 82) connected to athrottle shaft 80 that supports thethrottle valve 60. With this configuration, the output of themotor 70 is reduced in speed in accordance with gear ratios of thegears throttle shaft 80 to open and close thethrottle valve 60. One of the characteristics of this embodiment is that themechanism 72 is configured to open and close thethrottle valve 60 within a range between the fully-closed position and a position over or beyond the fully-opened position by predetermined opening, i.e., a position set over the fully-opened position in the opening direction by the predetermined opening, in response to the operation of themotor 70. This will be explained later. - The
throttle shaft 80 is installed on its circumference with a throttle return spring 84 (shown inFIG. 2 ) that is constituted of a torsion coil spring. One end of thespring 84 is connected to thefourth gear 82 attached to thethrottle shaft 80 and the other end thereof is connected to a hook pin 86 (shown inFIG. 2 ) projected in themotor case 52. Winding of thespring 84 is set in the direction in which thethrottle valve 60 is opened via thethrottle shaft 80. - The throttle valve opening/
closing mechanism 72 is connected with thechoke valve 62 through a choke valve opening/closing mechanism 90. Therefore, themotor 70 is connected to thethrottle valve 60 through themechanism 72 and to thechoke valve 62 through themechanisms - The choke valve opening/
closing mechanism 90 comprises anarm 94 that is attached to achoke shaft 92 supporting thechoke valve 62 for rotating theshaft 92, and alink 96 that connects thearm 94 with the mechanism 72 (precisely, thethird gear 78 thereof). - The
link 96 is supported to be rotatable about arotation shaft 100 in themotor case 52. Thelink 96 is provided at its end (one end) 96 a on thearm 94 side with afirst pin 96 b that extends upward inFIG. 2 . Thefirst pin 96 b is inserted through along hole 94 a bored in thearm 94. - The
link 96 is also provided at its end (the other end) 96 c on thethird gear 78 side with asecond pin 96 d that extends upward inFIG. 2 . Thesecond pin 96 d abuts on the circumference of thethird gear 78 at a portion not formed with teeth. The portion of the circumference of thethird gear 78 where no teeth is formed (i.e., where thesecond pin 96 d abuts) has a substantially disk shape and has a concavity. The portion of the circumference of thethird gear 78 where the concavity is formed is called the “first abutment portion” and assigned by 78 a. The remaining portion of the circumference of thethird gear 78 where no teeth is formed other than thefirst abutment portion 78 a is called the “second abutment portion” and assigned by 78 b. Positions formed with the first andsecond abutment portions third gear 78 will be described later. - As shown in
FIG. 2 , achoke return spring 102 is installed on the circumference of thechoke shaft 92. Thespring 102 is constituted of a torsion coil spring, similarly to thethrottle return spring 84. One end of thechoke return spring 102 is connected to thearm 94 and the other end thereof to ahook pin 104 that projects in themotor case 52. Winding of thespring 102 is set in the direction in which thechoke valve 62 is closed via thechoke shaft 92. - Since the choke valve opening/
closing mechanism 90 is configured to include thespring 102 that urges thechoke valve 62 in the closing direction (toward the fully-closed position), the urging force is transmitted to thelink 96 through thearm 94. As a result, counterclockwise force about therotation shaft 100 acts on thelink 96 so that thesecond pin 96 d of thelink 96 constantly abuts, as being pressed, on the circumference (i.e., the first orsecond abutment portion third gear 78. - Thus the one
end 96 a of thelink 96 is connected to thechoke shaft 92 through thefirst pin 96 b andarm 94, and theother end 96 c thereof to (abuts on) the throttle valve opening/closing mechanism 72 (precisely, the first orsecond abutment portion second pin 96 d. - Although not shown in the drawing, the
carburetor assembly 54 comprises a float chamber connected to a fuel tank, a main nozzle connected to the float chamber through a main jet and main fuel passage, and an idle port and a slow port both connected to a slow fuel passage that is branched from the main fuel passage. The main nozzle is installed at a position where it faces into theventuri 64 and the idle port and slow port are installed at positions where they face into the vicinity of thethrottle valve 60. - When the opening of the
throttle valve 60 is large, fuel is injected from the main nozzle owing to the negative pressure of the intake air passing through theventuri 64, thereby producing an air-fuel mixture. On the other hand, when the opening of thethrottle valve 60 is small, fuel is injected from the idle port or slow port owing to the negative pressure of the intake air passing through thethrottle valve 60. When thechoke valve 62 is closed, the negative pressure in theair intake passage 50 generated by descending stroke of thepiston 14 is increased, thereby increasing an amount of injected fuel and producing an enriched air-fuel mixture. The condition where the air-fuel mixture in theair intake passage 50 is enriched is hereinafter called the “rich air-fuel mixture condition.” - The
reference numeral 106 inFIG. 2 designates a fuel-cut solenoid valve (FS valve). A valve member (not shown) of theFS valve 106 is disposed between the float chamber and main jet and, when a coil (shown inFIG. 4 ; explained later) is energized, is closed for blocking passage of fuel. - Returning to the explanation of
FIG. 1 , the air-fuel mixture thus produced passes through theintake port 24 andintake valve 20 to be sucked into thecombustion chamber 16. The sucked air-fuel mixture is ignited by an spark plug (shown inFIG. 4 ; explained later) to burn and the resulting combustion gas is discharged to the exterior of theengine 10 through theexhaust valve 22,exhaust port 26, a muffler (not shown) and the like. - Thus, the
engine 10 has thethrottle valve 60 and chokevalve 62 each installed in theair intake passage 50 connected to thecombustion chamber 16, and air sucked in flows through theair intake passage 60 and mixes with fuel supplied by thecarburetor 46 to generate the air-fuel mixture that enters thecombustion chamber 16 of thecylinder 12 and is ignited to drive thepiston 14 to rotate thecrankshaft 30 to be connected to a load such as a generator. - An engine
speed setting switch 110 is installed to be manipulated by the operator and produces an output or signal indicative of desired engine speed in response to the manipulation by the operator. The outputs of the above-mentionedtemperature sensor 28,power coil 40,pulsar coil 42 and the enginespeed setting switch 110 are sent to an electronic control unit (ECU) 112 that is constituted as a microcomputer. - A
combination switch 114 is also installed to be manipulated by the operator. Thecombination switch 114 is connected to theECU 112. Based on the operator's manipulation of thecombination switch 114 and the other inputs, theECU 112 controls the operation of the engine 10 (e.g., the operation of the electric motor 70). -
FIG. 4 is an explanatory view showing the configuration of theECU 112 and thecombination switch 114. - As shown in
FIG. 4 , theECU 112 is equipped with arectification circuit 116, engine speed (NE)detection circuit 120 andcontrol circuit 122. The output of thepower coil 40 is inputted to therectification circuit 116, where it is converted to 12V direct current to be supplied as operating power to the components of theengine 10, such as theECU 112, through a circuit (not shown). The output of thepower coil 40 is also sent to the enginespeed detection circuit 120, where it is converted to a pulse signal. The pulse signal is inputted to thecontrol circuit 122 for detecting the engine speed. TheECU 112 is further equipped with asignal shaping circuit 124 and anignition circuit 126. The output of thepulsar coil 42 is inputted to thesignal shaping circuit 124, where it is formed as the ignition signal synchronous with rotation of thecrankshaft 30 and then sent to theignition circuit 126 andcontrol circuit 122. - The
combination switch 114 comprises first andsecond switches 114 a, 114 b. InFIG. 4 , the solid lines indicate the state of theswitches 114 a, 114 b when thecombination switch 114 is in the OFF position and the imaginary lines indicate their state when it is in the ON position. - The
first switch 114 a is interposed between the FS coil (now assigned by 130) and the FS valve (precisely, the valve thereof) 106. When the second switch 114 b is turned ON, the 12V direct current generated from the output of thepower coil 40 is inputted to thecontrol circuit 122 and a DC/DC converter 132. The DC/DC converter 132 is connected to the primary coil of anignition coil 136 through acapacitor 134 for charging thecapacitor 134. The secondary coil of theignition coil 136 is connected to the spark plug (now assigned by 140) and thecapacitor 134 is grounded via athyristor 142. - The
ignition circuit 126 applies current to the gate of thethyristor 142 in response to an ignition signal from thesignal shaping circuit 124 orcontrol circuit 122, so that thecapacitor 134 discharges to energize the primary coil of theignition coil 136. The resulting high voltage generated in the secondary coil produces spark between electrodes of thespark plug 140, thereby igniting the air-fuel mixture in thecombustion chamber 16. - The above-mentioned
temperature sensor 28 and enginespeed setting switch 110 are connected to thecontrol circuit 122. Based on the outputs of thetemperature sensor 28, enginespeed setting switch 110, enginespeed detection circuit 120 and the like, thecontrol circuit 122 determines desired openings of thethrottle valve 60 and chokevalve 62 and outputs control signals in accordance with the determined desired openings to amotor driver 144 so as to operate themotor 70, thereby opening and closing thevalves engine 10. - When the
combination switch 114 is put in the ON position by the operator, thefirst switch 114 a is turned OFF to cut off the supply of operating current to theFS valve 106. TheFS valve 106 is normally open, so that cutting off the supply of operating current enables jetting of fuel from thecarburetor 46. On the other hand, when the second switch 114 b is turned ON and therecoil starter 44 is operated, the resulting rotation of thecrankshaft 30 causes thepower coil 40 andpulsar coil 42 to produce outputs. As a result, 12V direct current and an ignition signal are produced (shaped) to activate theECU 112 and start theengine 10. - When the
combination switch 114 is put in the OFF position, the second switch 114 b is turned OFF and the supply of operating current to thecontrol circuit 122 is cut off, whereby thecontrol circuit 122 terminates ignition to stop theengine 10, and thefirst switch 114 a is turned ON to interconnect theFS coil 130 and theFS valve 106, thereby performing fuel cutoff. In other words, since rotation of thecrankshaft 30 does not stop immediately after ignition is terminated, theFS coil 130 continues to generate electricity and accordingly theFS valve 106 receives operating current from theFS coil 130 and is closed (i.e., fuel cutoff is performed) for a certain period. - Next, the opening and closing operation of the
throttle valve 60 and chokevalve 62 will be explained with focus on the operation of themotor 70, throttle valve opening/closing mechanism 72 and choke valve opening/closing mechanism 90 with reference toFIGS. 3 and 5 onward. -
FIG. 5 is an explanatory view showing the characteristics of the opening and closing operation of thethrottle valve 60 and chokevalve 62. - In order to operate the
throttle valve 60 to the fully-closed position, themotor 70 rotates thethrottle shaft 80 through the first tofourth gears mechanism 72 so as to close thethrottle valve 60 to the fully-closed position shown inFIGS. 3 and 5A . As can be seen inFIG. 3 , at this time, thesecond pin 96 d of thelink 96 abuts on thesecond abutment portion 78 b of thethird gear 78 and thechoke valve 62 is fully opened. - In order to operate the
throttle valve 60 from the fully-closed position to the fully-opened position, themotor 70 operates the first tofourth gears FIG. 6 to rotate thethrottle shaft 80 counterclockwise, thereby opening thethrottle valve 60 to the fully-opened position. At this time, since thesecond pin 96 d, while sliding to a position near thefirst abutment portion 78 a, remains abutting on thesecond abutment portion 78 b, as can be seen inFIG. 5B , thechoke valve 62 is held at the fully-opened position. Thus, when thethrottle valve 60 is positioned between the fully-closed position and the fully-opened position, themechanism 90 holds thechoke valve 62 at the fully-opened position. - When the
choke valve 62 is closed for producing the rich air-fuel mixture at engine start or the like, themotor 70 operates themechanism 72 to displace thelink 96 which moves in response thereto and rotate thechoke shaft 92, thereby opening and closing thechoke valve 62. Specifically, themotor 70 operates the first tofourth gears FIG. 7 to further rotate thethrottle shaft 80 counterclockwise, thereby opening thethrottle valve 60 to a position over or beyond the fully-opened position by predetermined opening a, which position is hereinafter called the “over-fully-opened position.” - At this time, the
second pin 96 d slides to thefirst abutment portion 78 a by the rotation of thethird gear 78. It causes thelink 96 to displace or rotate about therotation shaft 100 in the counterclockwise direction, so that thefirst pin 96 b, while sliding in thelong hole 94 a, displaces thearm 94. The displacement of thearm 94 makes thechoke shaft 92 rotate clockwise in the drawing, thereby closing thechoke valve 62 to the fully-closed position as shown inFIG. 5C . - Thus, the locations in the
third gear 78 formed with the first andsecond abutment portions second pin 96 d abuts on thesecond abutment portion 78 b (as shown, for example, inFIGS. 3 and 6 ), thechoke valve 62 is positioned at the fully-opened position, while thethird gear 78 is rotated clockwise in the drawing by themotor 70, and when thesecond pin 96 d abuts on thefirst abutment portion 78 a (as shown inFIG. 7 , for example), thechoke valve 62 is positioned at the fully-closed position. - As shown in
FIGS. 5A to 5C , the choke valve opening/closing mechanism 90 opens and closes thechoke valve 62 in response to the movement of the throttle valve opening/closing mechanism 72. More specifically, when thethrottle valve 60 is positioned between the fully-closed position and the fully-opened position, themechanism 90 holds thechoke valve 62 at the fully-opened position, and when thethrottle valve 60 is positioned between the fully-opened position and the over-fully-opened position, it opens and closes thechoke valve 62 within a range between the fully-opened position and the fully-closed position. - In the foregoing, the movement of the
choke valve 62 is explained using two kinds of positions, i.e., the fully-opened position and the fully-closed position. Since thefirst abutment portion 78 a is formed in the concave shape, thechoke valve 62 can be regulated to achieve a given opening by appropriately regulating a position where thesecond pin 96 d abuts on thefirst abutment portion 78 a. In other words, thechoke valve 62 can be opened and closed between the fully-opened position and the fully-closed position by properly regulating the opening of thethrottle valve 60 between the fully-opened position and the over-fully-opened position. - Next, the explanation will be made on the operation of the
motor 70 of opening and closing thethrottle valve 60 and chokevalve 62 at starting of theengine 10. -
FIG. 8 is a flowchart showing the processing of this operation of themotor 70 executed by theECU 112. - The illustrated program is executed only once at engine start. The
throttle valve 60 and chokevalve 62 are positioned as shown inFIGS. 7 and 5C before theengine 10 is started, specifically thethrottle valve 60 is at the over-fully-opened position due to the urging force by thethrottle return spring 84 and thechoke valve 62 is at the fully-closed position by thechoke return spring 102. - When the
combination switch 114 is put in the ON position and therecoil starter 44 is manipulated by the operator and successively thepower coil 40 starts generating power to activate theECU 112, the processing begins. - In S10, the operation of the
motor 70 is controlled so as to move (open and close) thethrottle valve 60 between the over-fully-opened position and the fully-opened position. Thethrottle valve 60 is moved as mentioned above to open and close thechoke valve 62 between the fully-closed position and the fully-opened position, as shown inFIGS. 5B , 5C. As a result, the air-fuel mixture in theair intake passage 50 is made rich (i.e., the rich air-fuel mixture condition is established), thereby improving the starting performance of theengine 10. - In S12, it is determined whether choking is required, i.e., whether the warm-up operation has been completed and the rich air-fuel mixture condition should be terminated. The determination in S12 is made based on the output of the engine
speed detection circuit 120 and, when the engine speed exceeds a predetermined value (e.g., 3000 rpm), it is discriminated that the choking is not required. - When the result in S12 is No, the program returns to S10 and when the result is Yes, the program proceeds to S14, in which the normal control of the
throttle valve 60 is conducted to terminate the rich air-fuel mixture condition, which is produced by thechoke valve 62. Specifically, the operation of themotor 70 is controlled so as to move thethrottle valve 60 between the fully-closed position and the fully-opened position (i.e., move thethrottle valve 60 at desired opening for maintaining the desired engine speed inputted through the engine speed setting switch 110). Since thethrottle valve 60 is moved between the fully-closed position and the fully-opened position, as shown inFIGS. 5A , 5B, thechoke valve 62 is held at the fully-opened position, thereby terminating the rich air-fuel mixture condition produced by thechoke valve 62. - Next, the explanation will be made on the opening and closing operation of the
throttle valve 60 and chokevalve 62 when theengine 10 is stopped. -
FIG. 9 is a flowchart showing the processing of this operation of themotor 70 executed by theECU 112. The illustrated program is executed at predetermined interval, e.g., 100 milliseconds. - In S100, it is determined whether an instruction to stop the
engine 10 is inputted, specifically thecombination switch 114 is put in the OFF position. When the result in S100 is No, the remaining steps are skipped and when the result is Yes, the program proceeds to S102, in which the operation of themotor 70 is controlled so that thethrottle valve 60 is moved (opened) to the over-fully-opened position. Thethrottle valve 60 is thus moved to close thechoke valve 62 to the fully-closed position, as shown inFIG. 5C , for preparing for the next engine start. - As described above, since the engine according to the first embodiment is thus configured, it becomes possible to move the
choke valve 62 by themotor 70 adapted to move thethrottle valve 60, i.e., move both thethrottle valve 60 and thechoke valve 62 solely by themotor 70. Owing to this configuration, thechoke valve 62 can be moved without the need of another motor, saving space to be required for installment of another motor. Further, an electric motor for the choke valve, an associated motor driver (drive circuit), which are utilized in the prior art '838 and indicated by imaginary lines inFIG. 4 , and other equipment such as a harness can be removed, thereby achieving decrease in power consumption and cost. - A general-purpose internal combustion engine according to a second embodiment of the invention will be explained.
-
FIG. 10 is a view, similar toFIG. 3 , but showing a carburetor of the engine according to the second embodiment when thecover 66 of themotor case 52 is removed. Constituent elements corresponding to those of the first embodiment are assigned with the same reference symbols as those in the first embodiment and will not be explained. - The explanation will be made with focus on points of difference from the first embodiment.
- In the second embodiment, as shown in
FIG. 10 , themotor case 52 is installed therein with a choke valveopening regulating mechanism 146 for regulating opening of thechoke valve 62. Themechanism 146 comprises a thermo-wax having awax section 146 a filled with wax which expands and contracts in response to ambient temperature (precisely, wax which expands in its volume with increasing ambient temperature, while contracting with decreasing ambient temperature; not shown), arod 146 b which is connected to thewax section 146 a and linearly displaces in response to the expansion/contraction of wax, adrive pin 146 d which is connected to thewax section 146 a through therod 146 b and aflange 146 c and linearly displaces in response to the displace of therod 146 b, and acase 146 e housing those components.FIG. 10 shows themechanism 146 when the wax is contracted. - A
tip 146 d 1 of thedrive pin 146 d projects toward the exterior through ahole 146 e 1 formed in thecase 146 e and can abut on the choke valve opening/closing mechanism 90 (i.e., thelink 96 thereof, more precisely, aside surface 96 e between therotation shaft 100 and end 96 a). Thedrive pin 146 d is normally urged by areturn spring 146 f in the direction of housing thedrive pin 146 d in thecase 146 e, i.e., of shortening the projecting amount (length) L of thetip 146 d 1 (in the downward direction in the drawing). Therefore, the projecting amount L of thedrive pin 146 d is made minimum by the urging force of thereturn spring 146 f when the wax is contracted (i.e., is not expanded) as shown inFIG. 10 . - The
mechanism 146 is further equipped with aheater 146 g for heating thewax section 146 a. Although not illustrated, theheater 146 g is composed of a heating wire made of a nichrome wire etc., an insulating material covering the wire, a protection pipe and the like. Theheater 146 g is thus an electric heater that generates heat when being supplied with power current as operating power from thepower coil 40. The operation of theheater 146 g is controlled by the ECU 112 (i.e., thecontrol circuit 122 thereof) as indicated by imaginary lines inFIGS. 1 , 4. - The operation of the choke valve
opening regulating mechanism 146 will be explained with reference toFIGS. 10 to 12 . -
FIG. 11 shows themechanism 146 when the wax is contracted andFIG. 12 shows that when the wax is expanded. It should be noted that thethrottle valve 60 is at the over-fully-opened position inFIGS. 11 , 12. - In the
mechanism 146, when the ambient temperature is relatively low, i.e., lower than operating temperature of themechanism 146 which is the thermo-wax, the wax of thewax section 146 a is contracted and it makes the projecting amount L of thedrive pin 146 d minimum. At this time, as shown inFIGS. 10 , 11, thedrive pin 146 d does not abut or slightly abuts on thesurface 96 e of thelink 96. In other words, when the wax is contracted, thetip 146 d 1 of thedrive pin 146 d does not abut on thesurface 96 e under condition where thelink 96 holds thechoke valve 62 either at the fully-opened position (FIG. 10 ) or at the fully-closed position (FIG. 11 ). - When the ambient temperature increases due to exhaust heat of the
engine 10 or heat generated by theheater 146 g and becomes higher than the operating temperature, as shown inFIG. 12 , the wax is expanded to push therod 146 b andflange 146 c upward in the drawing. As a result, thedrive pin 146 d acts against the urging force of thereturn spring 146 f and is displaced upward in the drawing, thereby increasing the projecting amount L. The operating temperature is, for instance, set to 70° C. - Therefore, when the
drive pin 146 d is displaced due to the expansion of wax with thechoke valve 62 being at the fully-closed position (FIG. 11 ), as shown inFIG. 12 , thedrive pin 146 d presses thesurface 96 e of thelink 96, whereby thelink 96 is displaced or rotated clockwise about therotation shaft 100. Accordingly, thesecond pin 96 d is moved apart from the circumference of thethird gear 78 and thefirst pin 96 b displaces thearm 94, while sliding in thelong hole 94 a. The displacement of thearm 94 causes thechoke shaft 92 to rotate counterclockwise in the drawing so as to open thechoke valve 62 to the fully-opened position. Thus thedrive pin 146 d drives the choke valve opening/closing mechanism 90 (i.e., thelink 96,arm 94 and the like) in response to the expansion/contraction of the wax, thereby regulating the opening of thechoke valve 62. - As described in the foregoing, the second embodiment is configured such that the
choke valve 62 is opened and closed by the choke valve opening/closing mechanism 90 that operates in response to the operation of the throttle valve opening/closing mechanism 72, and the opening of thechoke valve 62, which is opened and closed by themechanism 90, can be regulated by using the choke valveopening regulating mechanism 146 in response to ambient temperature. - Next, the explanation will be made on the opening and closing operation of the
throttle valve 60 and chokevalve 62 at starting of theengine 10. -
FIG. 13 is a flowchart similar toFIG. 8 , but showing the processing of this operation of the actuator executed by theECU 112. Note that it is assumed theengine 10 is started in the so-called “cold start” manner after a specific time period has elapsed since the last engine stop, ambient temperature around the choke valveopening regulating mechanism 146 is relatively low and the wax is contracted. - The processing of the steps of S200, S202 is conducted similarly to the first embodiment. When the result in S202 is No, the program returns to S200, i.e., the processing of S200 is repeated until the determination that the choking is not required is made. At this time, the exhaust heat of the
engine 10 increases with increasing engine speed. When the ambient temperature around themechanism 146 rises to the operating temperature or more due to the exhaust heat of theengine 10, the wax is expanded to gradually project thedrive pin 146 d. - The
drive pin 146 d displaces thelink 96 so as to gradually rotate thechoke valve 62 in the opening direction, i.e., it decreases fuel injection quantity as ambient temperature increases along with increase in the engine speed, thereby making the rich air-fuel mixture leaner gradually. Thus, during a period until completing the heating operation after activating theECU 112, the opening of thechoke valve 62 is regulated by themechanism 146 in response to ambient temperature. - When the result in S202 is Yes, the program proceeds to S204, in which the
heater 146 g starts being supplied with power to heat thewax section 146 a. The resulting further expansion of wax moves (projects) thedrive pin 146 d furthermore and forcibly opens thechoke valve 62 to the fully-opened position, thereby terminating the rich air-fuel mixture condition produced by thechoke valve 62. - In S206, the normal control of the
throttle valve 60 is conducted. Specifically, the operation of themotor 70 is controlled so as to move thethrottle valve 60 between the fully-closed position and the fully-opened position. Since thethrottle valve 60 is thus moved, thechoke valve 62 is held at the fully-opened position, and it is held at the fully-opened position also by thedrive pin 146 d of themechanism 146, so it becomes possible to prevent thechoke valve 62 from closing while theengine 10 is in operation. - Next, the explanation will be made on the opening and closing operation of the
throttle valve 60 and chokevalve 62 when theengine 10 stops. -
FIG. 14 is a flowchart similar toFIG. 9 , but showing the processing of this operation of the actuator executed by theECU 112. - In S300, it is determined whether an instruction to stop the
engine 10 is inputted. When the result is No, the remaining steps are skipped and when the result is Yes, the program proceeds to S302, in which power supply to theheater 146 g is cut off to stop heating thewax section 146 a. - The program then proceeds to S304, in which the operation of the
motor 70 is controlled so that thethrottle valve 60 is moved (opened) to the over-fully-opened position. Since thethrottle valve 60 is thus moved, thelink 96 of the choke valve opening/closing mechanism 90 is operated to close thechoke valve 62 to the fully-closed position. However, the wax is still in expanded status because the power supply to theheater 146 g has been just cut off in S302. As a result, thedrive pin 146 d projected due to the expansion of wax remains abutting on thelink 96 and thechoke valve 62 is held at the fully-opened position by thedrive pin 146 d. Specifically, thechoke valve 62 is not closed to the fully-closed position immediately after theengine 10 stops. - Therefore, even when the
engine 10 is hot-started, i.e., theengine 10 is restarted after elapse of a short period since the last stop, thechoke valve 62 stays at the fully-opened position or thereabout, thereby enabling to start theengine 10 without enriching air-fuel mixture excessively. - When a specific time period elapsed and ambient temperature around the
mechanism 146 lowered, the wax is contracted, resulting in gradual decrease in the projecting amount L of thedrive pin 146 d. As shown inFIG. 11 , it causes thechoke valve 62 to close to the fully-closed position for preparing for the next engine start. - As described in the foregoing, since the engine according to the second embodiment is thus configured, it becomes possible to prevent the air-fuel mixture from being enriched by opening the
choke valve 62 when ambient temperature is relatively high in a case of, for example, hot start, specifically, thechoke valve 62 can be regulated at appropriate opening in response to ambient temperature, thereby improving fuel efficiency. - The remaining configuration and effects are the same as those in the first embodiment and will not be explained.
- A general-purpose internal combustion engine according to a third embodiment of the invention will be explained.
-
FIG. 15 is a perspective view showing the vicinity of theair intake passage 50 of theengine 10 according to the third embodiment. Constituent elements corresponding to those of the first embodiment are assigned with the same reference symbols as those in the first embodiment and will not be explained. - The explanation will be made with focus on points of difference from the first embodiment. In the third embodiment, fuel-cut is conducted using a fuel-
cut needle valve 150 in place of theFS valve 106, and theneedle valve 150 is moved by thearm 94. Thechoke valve 62 is manually manipulated by the operator in the third embodiment. - Explaining specifically, the
needle valve 150 is connected to thearm 94 and ajet orifice 152 a of amain nozzle 152 can be sealed in response to rotation (displacement) of thearm 94. More specifically, when thethrottle valve 60 is at a position between the fully-closed position and the fully-opened position, theneedle valve 150 is positioned to make thejet orifice 152 a open for enabling fuel to inject from themain nozzle 152. On the other hand, when thethrottle valve 60 is moved to the over-fully-opened position, thearm 94 is rotated to move theneedle valve 150 downward in the drawing so as to seal thejet orifice 152 a, thereby cutting off supply of fuel. - Owing to this configuration, when the
throttle valve 60 is moved between the fully-closed position and the fully-opened position, i.e., thethrottle valve 60 is normally operated, theneedle valve 150 is positioned to make thejet orifice 152 a open, thereby enabling fuel to inject from themain nozzle 152. In a case where thethrottle valve 60 is configured to move to the over-fully-opened position when theengine 10 is stopped, theneedle valve 150 is moved downward so as to seal thejet orifice 152 a, thereby cutting off fuel supply. - As described in the foregoing, the engine according to the third embodiment is configured such that the
motor 70 moves both thethrottle valve 60 and the fuel-cut needle valve 150. With this, in a case of additionally installing an automatic fuel cut-off device in theengine 10, theneedle valve 150 can be moved without the need of another electric motor, saving space to be required for installment of a motor for theneedle valve 150. - The remaining configuration and effects are the same as those in the first embodiment and will not be explained.
- As stated above, the first to second embodiments are configured to have a general-purpose internal combustion engine having a throttle valve (60) and a choke valve (62) each installed in an air intake passage (50) connected to a combustion chamber (16), air sucked in flowing through the air intake passage mixes with fuel to generate an air-fuel mixture that enters the combustion chamber of a cylinder (12) and ignited to drive a piston (14) to rotate a crankshaft (30) to be connected to a load, comprising: an actuator (electric motor 70), a throttle valve opening/closing mechanism (72) connected to the actuator to open/close the throttle valve; and a choke valve opening/closing mechanism (90) connected to the throttle valve opening/closing mechanism to open/close the choke valve in response to operation of the throttle valve opening/closing mechanism. With this, it becomes possible to move the
choke valve 62 by themotor 70 for driving thethrottle valve 60, i.e., move both thethrottle valve 60 and thechoke valve 62 solely by themotor 70. - In the engine, the throttle valve opening/closing mechanism opens/closes the throttle valve within a range between a fully-closed position and an over-fully-opened position over a fully-opened position by predetermined opening a in response to the operation of the actuator, and the choke valve opening/closing mechanism holds the choke valve at a fully-opened position when the throttle valve is positioned between the fully-closed position and the fully-opened position, while opening/closing the choke valve within a range between the fully-opened position and a fully-closed position when the throttle valve is positioned between the fully-opened position and the over-fully-opened position. With this, it becomes possible to move both the
throttle valve 60 and thechoke valve 62 solely by themotor 70 further reliably. - In the engine, the throttle valve opening/closing mechanism comprises a plurality of gears (74, 76, 78, 82). With this, the throttle valve opening/closing mechanism can be simple in structure.
- In the engine, the throttle valve opening/closing mechanism comprises at least a first gear (74) connected to an output shaft (70S) of the actuator and a second gear (76) engaged with the first gear. With this, the throttle valve opening/closing mechanism can be simple in structure.
- In the engine, the choke valve opening/closing mechanism comprises a link (96) connected at its one end with a choke shaft (92) that supports the choke valve and at its other end with the throttle valve opening/closing mechanism, the link being adapted to displaced in response to the operation of the throttle valve opening/closing mechanism to rotate the choke shaft to open/close the choke valve. With this, the opening of the
choke valve 62 can be regulated with simple structure, thereby saving space further. - The engine according to the second embodiment further includes: a choke valve opening regulating mechanism that regulates opening of the choke valve opened/closed by the choke valve opening/closing mechanism in response to ambient temperature. With this, it becomes possible to regulate the
choke valve 62 at appropriate opening in response to ambient temperature, thereby improving fuel efficiency. - In the engine according to the second embodiment, the choke valve opening regulating mechanism comprises a wax section (146 a) filled with wax that is adapted to expand/contract in response to the ambient temperature, a drive pin (146 d) connected to the wax section, the drive pin driving the choke valve opening/closing mechanism in response to expansion/contraction of the wax to regulate the opening of the choke valve. With this, the opening of the
choke valve 62 can be regulated with the simple structure, thereby saving space further. - In the engine according to the second embodiment, the choke valve opening/closing mechanism further includes a heater (146 g) that heats the wax section. With this, it becomes possible to hold the
choke valve 62 at the fully-opened position after the warm-up operation is completed by heating thewax section 146 a by theheater 146 g and driving the choke valve opening/closing mechanism 90 through thedrive pin 146 d utilizing the expansion of wax, i.e., to forcibly hold thechoke valve 62 at the fully-opened position after the warm-up operation. Therefore, it becomes possible to reliably prevent thechoke valve 62 from closing while theengine 10 is in operation. Also, even when theengine 10 is hot-started, i.e., theengine 10 is restarted after elapse of a short period since the last stop, thechoke valve 62 stays at the fully-opened position or thereabout, thereby enabling to further improve fuel efficiency without enriching air-fuel mixture excessively. - The engine according to the second embodiment further includes: a heating stopper that stops the heater from heating the wax section when an operator inputs an instruction to stop the engine (S302). With this, it becomes possible to efficiently heat the
wax section 146 a in response to the operating condition of theengine 10. - The engine according to the first to third embodiments further includes: an actuator controller that controls operation of the actuator such that the throttle valve is opened to the over-fully-opened position when an operator inputs an instruction to stop the engine (S304). With this, it becomes possible to close the
choke valve 62 to the fully-closed position when theengine 10 stops, thereby improving the starting performance of theengine 10. - In the engine according to the first to third embodiments, since the actuator is an electric motor, the above-mentioned effects can be achieved with simple structure.
- It should be noted that, although the actuator (motor 70) for opening and closing the
throttle valve 60 and the like is exemplified as a stepper motor in the foregoing description, it can instead be any of various other kinds of electric motor, electromagnetic solenoid, or hydraulic equipment that is operated by driving its pump by a motor. - It should also be noted that, although in the foregoing the choke valve 62 (first and second embodiments) or the needle valve 150 (third embodiment) is moved in response to the operation of the throttle valve opening/
closing mechanism 72, a cock valve for performing fuel cut-off can instead be moved, for instance. - It should also be noted that, although fuel is supplied by the
carburetor 46, it is not limited thereto and an injector (fuel injection valve) can be disposed at theintake port 24 for supplying fuel. - Japanese Patent Application Nos. 2008-115605 and 2008-115606 both filed on Apr. 25, 2008, are incorporated herein in its entirety.
- While the invention has thus been shown and described with reference to specific embodiments, it should be noted that the invention is in no way limited to the details of the described arrangements; changes and modifications may be made without departing from the scope of the appended claims.
Claims (11)
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
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JP2008-115606 | 2008-04-25 | ||
JP2008-115605 | 2008-04-25 | ||
JP2008115605A JP2009264264A (en) | 2008-04-25 | 2008-04-25 | General-purpose internal combustion engine |
JP2008115606A JP5058058B2 (en) | 2008-04-25 | 2008-04-25 | General-purpose internal combustion engine |
Publications (2)
Publication Number | Publication Date |
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US20090266334A1 true US20090266334A1 (en) | 2009-10-29 |
US7854216B2 US7854216B2 (en) | 2010-12-21 |
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US12/383,168 Active US7854216B2 (en) | 2008-04-25 | 2009-03-20 | General purpose internal combustion engine |
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